I have a major weakness as a DM: I'm not very good at planning combats.
Current campaign is D&D 3.5, and I'm currently DM (We pass the duty around, and it's my turn).
I've a little background in live theater, and I love the Role-playing part of the game, so all too often my games turn into a semi-soap opera, with plot puzzles and personality issues between characters and "important people" in the game world.
In our game world there's a plague. I swear, we started this well before Covid came along, but like it or not it's the major problem in the game world.
The city of Seacrest is in trouble, a major outbreak and the city literally closed: Plague flags at the ports warning off ships, and all the gates sealed. Foodstuffs can come in, but it's an airlock kind of deal: Farmers get paid and leave their wagons outside. People from inside come out and get the wagons. Empty wagons, scrubbed and cleaned, are left outside later.
As is often the way, PCs have business in the city. They're on good terms with the young Duke (his father died in a pirate raid on the city), having helped him resolve a few small rebellions.
Okay, they weren't really rebellions. One was a group of pirates that had taken up residence in a border area military port that had been abandoned. The Duke hadn't had the troops or ships to take them head on, in their very defensible base, so the party went in to negotiate. Long story short, pardons were offered by the new Duke, and were accepted, approved by the King.
Another military base, a fortress in the northern mountains, controls a key pass, and thus trade with the north. Things didn't go quite so smoothly there. The man in charge doesn't trust the Duke.
Party used Scry and Divination to find out who had killed the fort commander's brother, a key factor in his rebellion. They had just captured a lot of men who tried to raid the town again, when it was weak. That was the same modus operandi of the last raid, timed to hit while the plague was running rampant.
They found that the captain of the ship where the commander's brother was killed was the "Commodore" (i.e. the now-pardoned pirate captain mentioned earlier.)
They're still trying to find a way to crowbar this situation into something they can use: They can't invite the northern commander to oversee the Commodor's execution because he can't be executed for his past crimes. He has a full pardon and is now in command of a part of the Ducal fleet, while the northern commander is still, technically an outlaw.
I'm thinking I need a nice combat-type encounter to shake them out of that fixation.
Party is six or seven PCs, 12th level or so, so swarming them with pirates, bandits, Rogues etc just doesn't work. They're head and shoulders above any mundane troops any government or rebel group can bring to bear.
I need to rationalize how/why they could encounter a group that can actually challenge them. Then, of course, I have to come up with such a group.
After that, actually running the scene is easy.